For the purposes of sections 84.350 to 84.860 all police officers, not including civilian employees and other than the chief, shall be assigned one of the following ranks: lieutenant colonel, major, captain, sergeant, master patrol officer, master detective, detective, investigator, or patrolman. Lieutenant colonels shall not exceed five in number, and other titles or designations for police officers may be used but they shall be equivalent in rank and salary to the ranks herein specified.